I'm experiencing very annoying behaviour using two nvidia cards.The second card simply freezes my system or gets REALLY REALLY slow. Currently I am using dual-head in my X configuration but I also tried Backstreet Ruby kernel patch to start two separate X Servers. Same problems there.

Currently I compiled and installed a vanilla kernel 2.6.12.5 on Debian Sarge but tried other distros and kernels as well. I have the following two cards: